Method and apparatus for the production of music



Jan. 7,-1936.

c. T. JACOBS 2,027,075 METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Original Filed Nov. s, 1933 INVENTOR Patented Jan. 7, 1936 PATENT OFFICE METHOD ANDAPPARATUS FOR THE, PRODUCTION OF MUSIC ,Charles T. Jacobs, New Providence Township,

Union County, N. J., assignor to Miessner Enventions, Inc., a corporation of New Jersey Application November 3, 1933, Serial No. 696,486 Renewed September 7, 1935 20 Claims.

This invention relates to musical instruments.

' particular form of such instrument, for example,

may comprise a plurality of tuned vibrators and mechanico-electric translating apparatus for translating their vibrations into electric oscillations, which oscillations are made to energize, and are translated into sound by, the electroacoustic translating device. I

A known type of mechanico-electric translating system for use in such instruments is the electrostatic type. Herein an electrostatic capacity is formed between the vibrators and a suitably placed conductive member; a charge rela tively incapable of rapid variation is maintained in this capacity; and the vibratory variation of the field of the so-charged capacity, produced by vibration of any of the vibrators, in turn produces across the capacity an oscillatory voltage component. My invention has been illustrated in connection with translating systems of this type;

while the broader aspects of the invention are generic to various types of translating systems, certain of the more specific aspects are peculiar to these particular system's.

In the U. S. Patent No. 1,906,607, issued to me May 2, 1933, there was disclosed and claimed an instrument wherein a group, of translating systems was employed, each system associated with each of a plurality of vibrators. The purpose of the use of a group of systems was as follows: The oscillations translated by each of the systems from any vibrator were of difierent waveform, by virtue of the difference in vibrational characteristics between the portions of the vibrator with which the systems were respectively 40 associated. Before translation into sound these oscillations were selectively combined in any of a plurality of phase and amplitude relationships at will, with the resultant production Of a wide range of sound tone qualities, or harmonic struc- 45 tures.

the purpose above described, improved in respect of simplicity and other characteristics.

Other and allied objects will more fully appear from the following description and the appended claims. 5

In the description reference is had to the accompanying drawing, of which:.

Figure 1 is a fractional view of a musical instrument, partly perspective and partly diagrammatic, illustrating a simple embodiment of my 10 invention;

Figure 2 is a perspective and diagrammatic view illustrating a preferred embodiment; and

Figure 3 is a perspective and diagrammatic view illustrating the embodiment of Figure 2 together 15 with a still further embodiment.

Reference being had to any of the figures, there will be seen a plurality of variously tuned strings l. By way of example only these have been shown excitable by hammers 2, and strung over 29 triangular bars 311 and 3b, it being understood that the active vibratory portion of each string is that lying between these bars. In slight spaced relationship to the. several strings I will be seen a conductive strip H; the strip ll may for example be cemented to the top of a bakellte or other insulating strip BI and this in turn secured in convenient manner to portions of the instrument not hercinnecessary to show. .Likewise in slight spaced relationship to the several strings 39 I will be seen conductive strips l2 and 13,-similar to conductive strip H and respectively cemented to insulating strips 62 and 63.

Consideration being given to any strip I I, I2, or l3, it will be understood thatbetween the strip as one electrode and any string I as the other a small electrostatic capacity exists. These stripto-string capacities are those in which there is to be maintained a charge relatively incapable of rapid variation and across which oscillatory 40 voltage components will be produced upon string vibration. It will be observed that the three strips II; I! and 13 are opposite respectively ditierent points along any string I, which points of course vibrate with respectively difierent wave- '45 forms; the oscillatory voltages appearing upon vibration of any string across the three capacities of strings to strip ll, of strings to strip l2, and of strings to string I: are therefore 0! respectively different waveforms. I shall hereinafter refer to the oscillatory voltage components appearing across each of these three capacities as a series of oscillations, it being understood that three such series are produced by any of the herein illustratedembodimehts OI my invention. Of course the use of apparatus appropriate to three series of oscillations is illustrative only, my invention not being limited to the production of any particular number of series.

The construction and operation thus far described are similar to those shown in the mentioned patent. Therein each of the three series of oscillations was applied to the input circuit of a separate vacuum tube; a separate transformer was employed in the output circuit of each of these tubes; and separate potentiometers, connected across the respective transformer secondaries and having variable portions mutually in series, were employed in the selective control and combination of the oscillations of the several series. Although this arrangement is fully-operative to produce the desired results it is susceptible of simplification and improvement, to which the instant invention is largely directed.

Reference is now had specifically to Figure 1.

The sourceof charges for the stringsto-strip capacities is the battery or other high voltage direct current source 5, which may be divided into two equal voltage sections 5a and 5b at the center point C. The means for maintaining the charges relatively incapable of rapid variation is the high resistance M, preferably of several megohms or more, connected between the source 5 (specifically the center point C thereof) and the strings (through the medium of theconductive bar 3a). It will be appreciated that the higher the value of the resistance It the more independent of oscillatory-capacity variations will be charges in the strings-to-strip capacities. The. charging circuit for the strings-to-strip H capacity is completed through potentiometer 3! connected across source 5 and having movable contact 2| connected to strip H. Similarly the charging circuits for the strings-to-strip l2 and strings-to-strip i3 capacities are completely respectively through potentiometer 32 with movable contact 22 and potentiometer 33 with movable contact 23. Preferably each of the potentiometers' has a total resistance valuewhich is a minor fraction of the value of resistance Hi.

The'amplitude of the oscillatory voltage variations at any frequency across any of the three strings-to-strip capacities is proportional to the D. C. voltage applied across that capacity, and the phase of the variations is dependent on the sign of the applied voltage. In Figure 1 it is readily seen that adjustment of any one of the potentiometers 3|, 32 and 3 3, by motion of its movable. contact progressively from one end of the potentiometer through the middle and to the other end, will control the voltage across the as- .sociated capacity progressively from half the voltage of the source 5 in one. sign, through zero, and to a like voltage in opposite sign. Thus by D. C. potential variation there is afforded in Figthe strings being connected directly to one extremity thereof and each of the strips l2 and I3 being connected to the other extremity through a system whose impedance to alternating currents is low compared to that of resistance l4. Thus the circuit of Figure 1 inherently combines. the oscillations of the several series.

The further elements of Figure 1 may be briefly described as follows: Tube 4 may be supplied with anode current from a tap T on the source 5 whereat the voltage is positive with respect to the center point C. Its cathode may be maintained at a potential slightly positive with respect point C by connection thereto through grid leak l6, resulting in the bias of the grid slightly negative with respect to the cathode. In'the anode circuit of the tube may be provided in cascade amplifier 6, potentiometer or volume control i, further amplifier B if desired, and loud-speaker or other electro-acoustic translating device 9. Obviously the combined oscillations are applied from resistance it through condenser 55 to the input circuit of tube 3; they may be amplified by that tube and by amplifiers 5 and 8; are controlled in respect of amplitude by volume control I; and finally energize, and are translated into sound by loudspeaker 9.

It is to be noted that the condenser l5 and grid the desired D. C. grid bias, although otherwise not,

noticeably harmful. It is. for the avoidance of this effect of leakage on grid bias that I employ the elements l5 and Hi.

In Figure 1 I have schematically shown electro static -shielding 55 connected to point C and surrounding the strings land tube 4 and elements connected or adjacent to strings and the grid ill, for the avoidance of sensitivity of these parts to leak 86 may if desired be omittedthe first by stray electrostatic fields. The strings l, however,

in the aggregate may represent a relatively large mass and surface disposed over a. relatively large area, and in Figure l are so connected in the circuit as to have a maximum sensitivity to the mentioned fields. These joint conditions as to the strings render somewhat rigorous the require-'- ments of completeness .and general excellence of the shielding 55, and this fact I consider a disadvantage df-the circuit of Figure 1. It is absent in Figure 2, to which attention is now directed."-

Herein the strings I are directly connected to the point C. The means for prevention of rapid charge variation are individual to the several strips 'H, l2 and l3, taking the form 'of high resistances 4|, 42 and 43, connected between the strips'and the movable contacts 2|, 22 and 23, re-

spectively. The several strips are connectedthrough condensers 5|, 52 and 53 respectivelyvto the grid eXtremit-y'of grid leak l6, which is connected as in Figurel from grid ID to the point C. It will be understood that the oscillations of tion, by the-movable contacts 2|, 22 and 23. As

a simplification these contacts have been shown as portions of a single potentiometer 34 connected across the source 5, it being understood that each of the contacts is movable over the whole range of the potentiometer without disturbance of the position of either of the other contacts. 75

each series are impressedthrough a. respective one of these condensers across the grid leak I5 shielded, but by virtue of their connection to the same point as the shielding actually aid the latter in its function. The joint conditions of less extensive sensitive portions and partial shielding effect of the strings considerably relax the requirements to be met by the shielding 55 in Figure 2.

A characteristic-advantageous particularly in respect of simplicity-of the circuits shown in Figures 1 and 2 is that the amplitude and phase control system for a plurality of oscillation series (e. g, iii-3243 or 34, with their movable contacts) is in shunt to a single circuit portion (e. g., source This characteristic may be present in other circuit arrangements, such for example as that wherein separate vacuum tubes are utilized for respectively difierent oscillation series. This has been illustrated in Figure 3.

as to strips 112 and 83 the arrangement of Figure 2 has been carried over into Figure 3, with two exceptions. One is that the condenser 53 connecting strip it to the grid ill (or grid extremity of grid leak 56) has been replaced by a condenser 53' connecting strip i3 to strip l2. The requirement being simply for a capacitive path from each strip to the grid (or grid leak extreniity), these paths may either be separate as in Figure 2 or cumulative as in Figure 3, wherein condenser forms a path active for both strips i2 iii'ie other exception is that the anode of tube 3 is coupled to amplifier 6 through an L- ermediate coupling circuit hereinafter described 4 12: view of the similarity of the involved parts to those of Figure 2, it will be obvious that the tube :3 functions toamplify oscillations of the two series strings-to-strip i2 and strings-to-strip l3 capacities. For the oscillations produced across the strings-to-strip it capacity, however, I provide another vacuum tube d having grid M. For thi may be provided grid leak l6, small esistance ii and condenser l8, respectively nalogcus in both connection andiunction to he elements it, it and ill associated with tube 3. *5 may be connected through condenser tne grid extremity of grid leak iii the opposite extremity. of which is connected to the point C. It will be understood, of course, that the oscillations produced across the strings-tostrip 5 l capacity are applied without phase or amplitude control through condenser 5! to the input circuit of tube i and are amplified by that tube, strip ii being connected through its resistance ll to a point of fixed potential in source 5.

A circuit is illustrated for coupling the anode circuits of each of tubes ti and Al to the amplifier t. This conveniently includes resistances 36 and respectively connected from the anodes of tubes :3 and G to tap T on source 5 and providing paths for the D. CLcomponents of the re- 'spective anode currents. Each of the resistances 38 and 355' preferably has a resistance value of several times the plate impedance of the associated tube. A transformer 44 is provided having secondary ill connected to amplifier 6i and having primary 39 with center tap C connected to a point in-source 5, preferably tap T. The lowereter 3B, the effects will be respectively produced across the are respectively designated as 48 and 49. Across the entire primary is shunted a potentiometer 38, provided with two movable contacts 31 and 31' each adjustable over the whole potentiometer range without disturbance of the position of the other. To these movable contacts are respectively connected the anodes of tubes 4 and 4', through respective condensers 35 and 35', whose function it is to confine the D. C. components of the anode currents to the paths 36 and 36' abovementioned.

It is contemplated that the amplifier 6 have a finite input impedance which is constant with varying frequency. A resistance 41, shown in Figure 3, may be employed to shunt any inherent input impedance which the amplifier may have, the value of resistance 41 being chosen low enough so that the eifectiveinput impedance of amplifier B (e. g., the inherent impedance and the actually included resistance 41 in parallel) shall meet the mentioned specification. The step-up ratio of each half of the primary 39 to the secondary 40 of the transformer 34 is conveniently made approximately equal to the square root of the ratio between effective amplifier input impedance and the output impedance of each of tubes 4 and 4'; and the inductance of each half of the primary 39 is desirably such that the inductive reactance at low frequencies is greater than such output impedance. Under these conditions, and considering the primary 39 apart from the preceding circuit, currents traversing either half of the primary encounter therein an effective impedance which is essentially resistive and approximately equal to the output impedance of either tube 3 or i. The total value of resist ance of the potentiometer 38 may conveniently be twice such output impedance. It will be understood that I do not specify the quantitative relations between the different circuit elements with any limiting purpose in mind, but rather that a useful example of such relations may be presented for aid in an understanding of the circuit function.

Momentarily assuming that only one of the contacts 31 and'ill is connected to the potentiometer 38, it will be apparent that with this contact centrally located on the potentiometer, oscillations passing thereto from the associated tube anode through the associated condenser will divide and flow equally in two 'paths. One of these is the upper portion of potentiometer 38 and half-primary 38; the other the lower portion of potentiometer 33 and the half-primary 88. These currents being equal, they will mutually cancel in the primary 39 as a whole, and no oscil-= lations will be induced in the secondary to. If the contact be adjusted to the top extremity of potentiometer 38, the oscillations will again divide, the respective paths now being the half- -primary E9 and the series path comprising the entire potentiometer 38 and the half-primary 48. The oscillations flowing in these two paths will again be in opposition to each other in the primary 39 as a whole; but because of the much higher impedance of the second path, only a minor fraction of the oscillations flows therein, and the opposition of the flow in the half-primary 49 by that in the half-primary =38 is relatively slight. There are therefore induced in the secondary BB oscillations of finite amplitude and a certain phase. Still again, if the contact be adjusted to the bottom extremity of potentiom- (iii) similar but opposite to till all.

those just discussed, and there will be induced in the secondary to oscillations of similar ampliture but of opposite phase to those last mentioned as induced therein. And at positions intermediate the three specially considered ones there will be induced in secondary to oscillations of respectively intermediate amplitudes and of phase dependent on the extremity of the potentiometer 38 to which the contact'is nearer. A control over oscillation phase and amplitude quite analogous in eflect to that obtained by the above described adjustment of sucha contact as 22!, 22 or 23 is thus obtained by adjustment of either contact 3! or 3?.

When both contacts 37 and 3? are connected to the potentiometer 38 as shown, the adjustment of one may cause some quantitative modification of the precise above described eiiects of adjusttiometer 36), the tubes 4 and d each pass to the coupling circuit a separate series of oscillations; and the oscillations of the two series are respectively controlledin respect of phase and amplitude by adjustments of contacts 3?. and 3'5, are combined in the coupling circuit, and in combined form appear across the secondary so and are passed therefrom to the amplifier 6. This statement remains true whento the input circuit of tube d is applied any particular combination of oscillations of two series (by virtue of any particular adjustment of contacts 22 and 23), this oscillation combination then itself being identifled as a series of oscillations. Thus in Figure 3 the amplitude and phase control system for a plurality of oscillation seriespotentiometer '38 with its movable contacts-is in shunt to the single circuit portion comprising the primary 39 of transformer do. While this potentiometer system has been illustrated for the control and combination of two series of oscillations, it is not limited in usefulness to this or any other particular number.

It will be understood that variations of the ar-' rangements herein shown and described may be means mpons'ive'to oscillatory, voltages across all of said capacities; and progressively adjustable means for varying the amplitudes and signs of the mean charges in said capacities.

Z Incombination in a musical instrument: a]

a plurality of capacities; 'means for producing oscillatory variation of said capacities at similar fundamental frequencies but with respectively different waveforms; means for charging said capacities; means for limiting changes of charges insaid-capacities by said oscillatory variations; means-responsive to oscillatory voltages across all of said capacities; and means for varying 'the' mean charges-in said capacities.

3. In. combination in a musical instrument: a

tuned vibrator; a plurality of electrodes respecrater tinned oscillations.

vibrating with difierent waveforms and forming with" said vibrator a plurality of vibration-varied capacities; means for charging said capacities;

means for limiting changes of charges in said capacities by vibrator vibration; means responsiveto oscillatory voltages across all of said capacities being electrically common; means for oscillatorily varying said capacities; capacity charging means, comprising meansior main-' taining the uncommon sides of said capacities at mean potential differences from said common side; means for limiting changes of charges in said capacities by said oscillatoryvariation; and

an electrical work circuit responsive to oscillatory voltages across said capacities, said circuit being capacitively connected to the uncommon side'of each of said capacities.

5. In combination in a musical instrument: a

tuned vibrator; a plurality of electrodes respectively associated with said vibrator and forming 3Q; 25

therewith a plurality of vibration-varied capacities; capacity charging-means, comprising means for maintaining said electrodes at mean potential diiierenc'es from said vibrator; means for limiting changes of charges in said capacities by vibrator vibration; and an electrical work circuit responsive to oscillatory voltages across said capacities, said'circuit being capacitively con-.

nected to said electrodes r 6. In the system of musical tone generation including the production of electric oscillations by the oscillatory variation, with similar fundamen-.-

cluding the translation into sound of said oscillations, the method of timbre control which consists in selectively controlling the amplitudes of the charges in the several said capacities and in combining oscillations appearing across-said ca.-

' pacities to produce said first mentioned oscillations. 7

' 7. In the system of 'musical tone generation including the production of electric oscillations by the oscillatory variation, with similar fundamental frequency but respectively difieren't waveforms, of a plurality of electrical capacities in each of which is maintained an electrical charge relatively independent of said variations and including the translation into sound of said oscillotions, the method of timbre control which consists in selectively controlling the signs of the charges in the several said capacities, and in combining oscillations appearing across said capacities to produce said .first mentioned oscil- I 8. In the systemof musical tone generation incIudingthe production oi electric oscillations by the oscillatory variation, with similar fundamen-' tal frequency but respectively difierenir wave forms, of a plurality of electrical capacities in sists in selectively controlling theamplitudes and si ns'oi the charges in theseveral said capacities, and in, combining oscillations appea: across said capacities to produce said first men 9. In a musical instrument including an electro-acoustic translating device and an electric system operative in the energization of said device: the combination of a plurality of oscillation sources adapted to produce a like plurality of seriesof electric oscillations all having the same fundamental frequency but having respectively different waveforms; means in shunt to a single portion of said system for controlling the phases of the oscillations of each of a plurality of said series; means for combining the so-controlled oscillations of said plurality of series; and means for supplying said combined oscillations to said electro-acoustic translating device to 'energize the same.

10. In a musical instrument including an electro-acoustic translating device and an electric system operative in the energization of said device: the combination of a plurality of oscillation sources adapted to produce a like plurality of series of electric oscillations all having the same fundamental frequency but having respectively different waveforms; means in shunt to a single portion of said system'for controlling the amplitudes and phases of the oscillations of each of a plurality of said series; means for combining the so-controlled oscillations of said plurality of series; and means for supplying said combined oscillations to said electro-acoustic translating device to .energize the same.

11. In a musical instrument including an electro-acoustic translating device and an electric system operative in the energization of said device: the combination of a tuned vibrator and means for vibrating the same to produce in different portions thereof vibrations having the same fundamental frequency but having respectively different waveformsf a plurality of mechanico-electric translating systems respectively associated with different portions of said vibrator and each adapted to produce a series of electric oscillations; means in shunt to a single portion of said system for controlling the phases of the oscillations of each of a plurality of said series; means for combining the so-controlled oscillations of said plurality of series; and means for supplying said combined oscillations to said electro-acoustic translating device to energize the same. i

12. In a musical instrument including an electro-acoustic translating device and an electric system operative in the energization of said device: the combination of a tuned vibrator and meansfor vibrating the same to produce in different portions thereof vibrations having the same fundamental frequency but having respectively different waveforms; a plurality of mechanico-electric translating systems respectively associated with different portions of said vibrator and each adapted to produce a series of electric oscillations; means in shunt to a single portion of said system for controlling the amplitudes oi the oscillations of each of a plurality of said series; means for combining the so-eontrolled oscillations of said plurality of series; and means for supplying said combined oscillations tosaid electro-acoustic translating device to energize the same.

13. In a musical instrument including an electro-acoustic translating device and anelectric system operative in the energizations of said tively different waveforms; a plurality of mechanico-electric translating systems respectively associated with different portions of said vibrator and each adapted to produce a series of electric oscillations; means in shunt to a single portion of said system for controlling the amplitudes and phases of the oscillations of each of a plurality of said series; means for combining the so-con-' trolled oscillations of said plurality of series; and

means for supplying said combined oscillations to said electro-acoustic translating device to energize the same.

14. In a musical instrument including an electro-acoustic translating device and an electric system operative in the venergization of said device: the combination of a tuned vibrator and means for vibrating the same to produce in different portions thereof vibrations having the same fundamental frequency but having respectively different waveforms; a plurality of conductive members respectively in spaced relationship to different portions of said vibrator and forming therewith electrical capacities oscillatorily varied by said vibrations, means for maintaining in the respective said capacities electrical charges relatively independent of said capacity variations; means in shunt to a single portion of said system for controlling the amplitudes of said charges; means for combining oscillations appearing across the several said capacities; and means for supplying said combined oscillations to said electro-acoustic translating device to energize the same. i

p 15. In a musical instrument including an electro-acoustic translating device and an electric system operative in the energization of said device; the combination of a tuned vibrator and means for vibrating the same to produce in different portions thereof vibrations having the same fundamental frequency but having respectively different waveforms; a plurality -of conductive members respectively in spaced relationship to difierent portions of said vibrator and forming therewith electrical capacities oscillatorily varied by said vibrations, means for maintaining in the respective said capacities electrical charges relatively independent of said'capacity variations; means in shunt toa single portion of said system for controlling the signs of said charges; means for combining oscillations appearing across the several said capacities; and means for supplying said combined oscillations to said electro-acoustic translating device to energize the same.

16. In a musical instrument including an elec- I tro-acoustic translating device and an electric system'operative in the energization of said device: the combination of a tuned vibrator and means for vibrating the same to produce in different portions thereof vibrations having the same fundamental frequency but having respectively different waveforms; a plurality of consaid system for controlling the amplitudes and signs of said charges; means for combining oscillations appearing across the several said capacities; and means for supplying said combined oscillations to said electro-acoustic translating device to energize the same.

H. In a musical instrument including an electrc-acoustic translating device and an electric system operative in the energization of said device: the combination of a tuned vibrator and means for vibrating the same to produce in different' portions thereof vibrations having the same fundamental frequency but having respectively difierent waveforms; a plurality of conductive members respectively in spaced relationship to different portions of said vibrator and forming therewith electrical capacities oscillatoriiy varied by said vibrations; a source of di rect current; a high resistance connected between said vibrator and a point in said source; a potentiometer system shunting said source and having adjustable contacts respectively connected to said conductive members; and means for supplying oscillations appearing across said resistance to said electro-acoustic translating device to energize the same.

18. In a musical instrument including an electro-acoustic translating device and an electric system operative in the energization of said device: the combination of a tuned vibrator and means for vibrating the same to produce in different portions thereof vibrations having the same fundamental frequency but having respectively difierent waveforms; a plurality of conductive members respectively in spaced relationship to difierent portions-of said vibrator and forming therewith electrical capacities oscillatorily varied by said vibrations; a source of direct current; a connection from said vibrator to a point in said source; a potentiometer system shunting said source and having adjustable contacts; high resistances connected between said conductive members and said adjustable contacts, respectively; means for combining oscillations appearing across the several said capacitiesand means for suppiying said combined oscillations to said acaaovs electro-acoustic translating device to energize the same.

19. In a musical instrument including an electro-acoustic translating device and an electric 'system operative in the energization of said 5 operatively connected to said electro-acoustic 15 translating device; a source of direct ciu'rent; connections from said vibrator to a point in said source and from an extremity of said work circuit to a point in said source; high resistance means connecting said conductive members with 0 said source; and capacitive means connecting all of said conductive members with the other extremity of said work circuit.

20. In a musical instrument including an electro-acoustic translating device and an electric 5 system operative in the energization of said device: the combination of a transformer having a primary winding and a center-tap on said winding and having a secondary winding operatively connected to said electro-acoustic translating device; a potentiometer system shunting said primary winding and having adjustable contacts; and a plurality of oscillation sources adapted to produce a like plurality of series of electric oscillations all having the same fundamental frequency but having respectively different waveforms, each of said sources being connected bev tween-said center-tap and a respective one of said movable contacts.

CHARLES "r. moons. m a 

